Stung into action by the Russian intervention in Ukraine and shock 2014 annexation of Crimea, NATO has boosted its resources and readiness to meet any new threat but its nervous former Soviet allies in the east are pushing for more.
Former Norwegian premier Stoltenberg said the 28-nation alliance's defence ministers had agreed at a meeting in Brussels on plans for an "enhanced forward presence in the eastern part of our alliance".
He spoke of a "more assertive Russia which has used force to change borders" and said that NATO, formed in the depths of the Cold War, now faced the "most challenging security environment in a generation."
The force will likely involve between 3,000 and no more than 6,000 troops, NATO diplomatic source said, although Stoltenberg gave no further details as the project must now go to the military planners to be fleshed out.
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Critics say the Ukraine crisis and the annexation of Crimea badly wrong-footed the alliance, which under-estimated Russia's ability to move so quickly and make such effective use of hybrid warfare.
Stoltenberg recalled that in response, NATO has already taken steps to boost its readiness by creating a very fast reaction force, setting up forward command centres and pre-positioning equipment so that reinforcements can hit the ground running.
Combined, the measures amount to what NATO dubs "modern deterrence," a doctrine meant to ensure that NATO can react quickly and flexibly to all emerging threats.
Other NATO member states have been reluctant to revert to what they see as a Cold War stand-off with Russia, especially when seeking Moscow's help to solve other conflicts such as in Syria.